1. Technical Field
The present invention relates to a sheet feeding apparatus used for automatically transporting a sheet, and an image forming apparatus and an image reading apparatus which include the sheet feeding apparatus.
2. Related Art
In general, an image forming apparatus such as a printer and an image reading apparatus such as a scanner include a sheet feeding apparatus which supplies a sheet from a placement surface of a sheet feeding tray to an image forming portion or an image reading portion. The sheet feeding apparatus includes a sheet feeding roller which abuts against a sheet and rotationally drives for automatically supplying the sheet placed on the placement surface.
Further, as is known, a sheet feeding apparatus generally includes an edge guide which abuts against a side edge of a sheet in the width direction to guide transport of the sheet. The edge guide includes a fixed guide and a movable guide so as to guide transport of a sheet depending on various kinds of sheet sizes.
Further, there is disclosed a sheet feeding apparatus on which a sheet feeding roller is arranged so as to abut against a surface of a sheet at the fixed guide side (see JP-A-2001-80761, for example).
In JP-A-2001-80761, a support axis to which a pickup unit is attached is supported on one side plate with a cantilever structure. To be more specific, in the sheet feeding apparatus disclosed in JP-A-2001-80761, a pickup unit is attached to a top end of the support axis extending from a fixed guide (side plate), and a sheet feeding roller is rotatably arranged on the top end of the pickup unit. With such a configuration, the sheet is transported while a surface of the sheet is pressed on the side where the fixed guide is located by the sheet feeding roller.
In the sheet feeding apparatus including the sheet feeding roller which abuts against a surface of a sheet at the fixed guide side and rotationally drives, the sheet has been transported in a state in which the sheet is tilted relative to the transport direction in some case. To be more specific, a force of transporting a sheet P is generated on one edge side of the sheet P in the width direction by a sheet feeding roller 8 located at the side of a fixed guide 6a as shown in FIG. 17 and FIG. 18. The sheet feeding roller 125 abuts against a surface of the sheet P and rotationally drives. However, when a sheet P having high elasticity such as cardboard or the like is transported, the other edge of the sheet P (that is, the side of a movable guide 23) where the sheet feeding roller 8 is not provided is lifted off from a placement surface 4 during transport of the sheet P in some case. There is a disadvantage that the sheet P is transported in a state in which the sheet P is tilted relative to the transport direction by a sheet feeding apparatus 102, if the sheet P is lifted off as described above.
In order to avoid such a disadvantage, it can be considered that an abutment member which abuts against a surface of a sheet is also provided on the side of the movable guide as in the same manner as the sheet feeding roller. Further, it can be considered that the abutment member which abuts against the surface of the sheet at the side of the movable guide is biased toward a placement surface by an elastic member, thus the surface of the sheet can be effectively pressed at the side of the movable guide by the abutment member.
However, in a case where the abutment member is biased toward the placement surface, when a sheet is to be placed on the placement surface, the sheet needs to be inserted between the placement surface and the abutment member. In such a case, when the sheet is set between the fixed guide and the movable guide and then the movable guide is moved so as to abut against the side edge of the sheet, the sheet inserted from the side of the fixed guide is interfered with the side surface of the abutment member provided on the movable guide in some case. Therefore, the sheet cannot be easily placed on the placement surface against which the abutment member is pressed.